1. Field of the Invention
The present invention relates to a process and an apparatus for the purification of organic compounds containing readily-blocking substances.
Specifically, the invention relates to a process and an apparatus which is advantageously used for the purification of, for example, (meth)acrylic acid, (meth)acrylic esters, maleic anhydride, phthalic anhydride and other organic compounds containing readily-blocking substances. The readily-blocking substances (hereinafter may be referred to as xe2x80x9ccloggy substancesxe2x80x9d) include insoluble solid matters and viscose matters such as slurry and polymer.
2. Description of the Related Art
Apparatus for use in the purification of a specific component from a mixture of plural components are classified, with respect to the way of contacting gas component with liquid component (gas-liquid contact) such as cross-current contact type shown in FIG. 1A, counter-current type shown in FIG. 1B, and shower-contact type shown in FIG. 1C.
The purification process of the cross-current contact type shown in FIG. 1A, uses the purification tower having trays 1 with downcomer 3 and weir 2 (dam baffle). The tray 1 has openings 1a through which gas is ascending and the gas is passed through liquid (or slurry) R being held on the tray 1. Thereby gas-liquid contact is performed.
The purification process of the counter-current type shown in FIG. 1B, uses the purification tower having trays 4 with openings 4a. The opening 4a is a orifice in the tray for gas-liquid contact. Gas is ascending through the openings 4a of the tray 4, and the gas is passed through liquid (or slurry) being held on the tray 4. The liquid on the tray 4 is descending thorough the openings 4a and the liquid is also contacting with the gas in the opening 4a and after passing through the opening 4a. Thereby gas-liquid contact is performed.
The purification process of the shower-contact type shown in FIG. 1C, use the purification tower having segmental baffles. Gas-liquid contact is performed when liquid falls from baffle window of an upper baffle 5 to a lower baffle 6 while gas is ascending counter-currently to the liquid.
Comparing gas-liquid contact efficiencies of the purification type FIGS. 1A to 1C, the cross-current contact type (1A) shows the highest efficiency, and the counter-current contact type (1B) shows the second highest efficiency. Accordingly, the cross-current contact type (1A) and the counter-current contact type (1B) are in wide use for purification.
However, when a substance to be purified is an organic compound containing cloggy substances, openings 1a (or openings 4a) of the trays 1 (or trays 4) used in the cross-current contact type and the counter-current contact type are readily blocked by the cloggy substances.
When such clogging occurs, the gas-liquid contact efficiency of the cross-current contact type and counter-current contact type is lowered. Also the clogging, which brought the difficulty in operating the purification tower, inhibits the flow of liquid and gas.
The build-up blockage of the openings must be removed by suspending an operation of the tower and the blockage is removed by manpower or by using chemical agents.
An object of the invention is to provide an apparatus for the purification of even an organic compound containing readily-blocking substance, which are capable of continuously purifying such an organic substance over the long time without discontinuing an operation.
The above object can be attained by a purification tower comprising:
(a) a shell; and
(b) a plurality of baffles, each of which is fixed to an internal surface of the shell,
(i) said each baffle having a flat upper surface and a plurality of openings are formed in each of the baffle so that liquid and gas pass through the openings;
(ii) any adjacent pair of the baffles are arranged so that a bottom of the shell is covered by the pair of the baffles viewing in an longitudinal direction of the shell.
Another object of the invention is to provide a process using the same which can attain the high gas-liquid contact efficiency.